The present invention relates generally to the field of digital radio communication systems and, more particularly, to the periodic registration procedure in a digital radio communication system used to identify and update the location and activity status of mobile radio communication devices within said system.
When a mobile station is powered up, its operational parameters within the network system must be determined. In general, the mobile station first goes through the process of selecting a candidate service provider. When a suitable candidate is determined, the mobile station then searches for service on a particular digital control channel (DCCH). Having found service on a DCCH, the mobile station then reads the service parameters from the fast broadcast control channel (FBCCH) before entering the digital control channel camping state. As part of continued service on a particular digital control channel (DCCH), the mobile station must periodically execute a registration which is transmitted to the base station. This periodic registration provides an update of location and activity status of the mobile station to the base station. This registration procedure applies to mobile stations on a DAMPS Digital Control Channel (DCCH) per Telecommunications Industry Association Standard IS 136.1, the entirety of which is hereby incorporated by reference.
In layer 3 communications, the Registration Parameters FBCCH message is mandatory and the data associated with this message is always transmitted to the mobile station by the base station on power up. The FBCCH includes many information elements. The information elements particularly affecting the registration function include the xe2x80x9cREG Periodxe2x80x9d and the xe2x80x9cREGID Parameters.xe2x80x9d The REG Period information element (REG Period IE) gives the registration period of the mobile station, expressed in increments of 94 superframes, and may vary from 94 to 48,128 superframes. That is, the mobile station is required to transmit a periodic registration to the base station after a certain multiple of 94 superframes have elapsed. Since a superframe is equivalent to approximately 640 milliseconds, 94 superframes represents approximately one minute. The REGID Parameters information element (REGID Parameters IE) includes the subelements REGID and REGID_PER. REGID is an updateable system clock internal to the mobile station ranging from 0 to 1,048,575 increments. An increment represents a fixed period of time determined as a function of REGID_PER. REGID_PER indicates how often REGID is incremented and is expressed in superframes. The REGID Parameters IE may be updated by the base station at any time and then transmitted to the mobile station via the FBCCH.
Layer 3 in the mobile station also includes the variable NXTREG which is the value that REGID must equal or exceed before the mobile station transmits a periodic registration to the base station. NXTREG is a permanent variable which remains stored in the mobile station even when the power is turned off. Following the current protocol outlined in IS 136.1, both NXTREG and REGID are required to be stored in the memory of the mobile station on power down of the unit.
When the mobile station is turned on or powered up, it will read the Registration Parameters from the FBCCH and then enter the DCCH camping state. The camping state refers to a state of readiness attained by the mobile station after initialization via the FBCCH, where it will remain as long as the mobile station is locked onto the best DCCH. The mobile station will leave this state only to process certain transactions such as power up, power down, an originated call, a terminated call, or a registration. A full description of the DCCH camping state is provided in IS 136.1, Section 6.2.3.
The REGID system clock is incremented by counting the number of superframes on the control channel. After each superframe is completed, the mobile station 16 determines whether the threshold amount of superframes, corresponding to the variable REGID_PER, has been reached. If the specified number of superframes is reached, the REGID system clock is incremented. Each time the REGID system clock is incremented, the Registration Procedure per IS 136.1, Section 6.3.7 is called. Within the Registration Procedure is the Periodic Registration Determination detailed in IS 136.1, Section 6.3.9. Periodic Registration Determination basically compares REGID (Current Registration ID) with NXTREG. If REGID is less than NXTREG, the mobile station returns to the camping state and awaits the next incrementation of REGID after the next fixed amount of superframes, as defined by REGID_PER, have elapsed. On the other hand, if REGID is greater than or equal to NXTREG, the mobile station is instructed to transmit a periodic registration to the base station. The REGID system clock is then reset and the procedure of tracking elapsed superframes begins anew.
In review, the previous method for determining registration timing of the mobile station outlined by IS 136.1 requires that the amount of elapsed superframes be compared to REGID_PER after each superframe. Also, the REGID system clock must be incremented and compared to NXTREG after every REGID_PER superframe increment. Thus, computational power requirements for the mobile station under this protocol are significantly high since calculations must be performed after every superframe and the REGID system clock constantly has to be checked and stored in memory.
The present invention provides a new method for determining the point at which the mobile station is required to transmit a periodic registration to the base station when the mobile station is locked onto a DAMPS Digital Control Channel. The REGID system clock in the mobile station is replaced with a timing mechanism termed REGID_PER_TMR. Instead of tracking the REGID system clock from zero to NXTREG, REGID_PER_TMR is a function of the NXTREG permanent variable and the REGID_PER variable transmitted in the Registration Parameters FBCCH message. Thus, REGID_PER_TMR is a specific time period calculated as a function of NXTREG and REGID_PER on power up of the mobile station and does not need to be stored within the memory of the mobile station. REGID_PER_TMR then functions as a countdown timer relative to NXTREG such that the mobile station automatically transmits a periodic registration upon expiration of REGID_PER_TMR. Since the REGID system clock has been eliminated, the value of REGID is calculated on an as-needed basis from other parameters.
It follows that, by eliminating the REGID system clock, the mobile station no longer needs to perform computations after every superframe to determine if the REGID system clock must be incremented. In addition, the mobile station does not need to determine if REGID is greater than NXTREG each time the REGID system clock is incremented. Thus, one object of the present invention is to lower the power consumption of the mobile station where Periodic Registration Determination is only performed after the expiration of REGID_PER_TMR instead of after every superframe.